Quebec Police confirmed five fatalities from the blaze on Thursday, while three dozen more remained unaccounted for as rescuers prepared to search through the night for more victims.

The search and an investigation into the cause of the fire were hampered by up to 30 centimeters (a foot) of ice covering the wreckage after water used to douse the fire froze.

The blaze at the 52-unit home, which housed around 50 to 60 elderly people, half of them more than 85 years old, broke out shortly after midnight.

"We could hear screaming from inside. The fire was intense, it was like a haystack on fire," witness and neighbor Pascal Fillion told.

By 1am, the building "was completely engulfed in flames, which were fanned by the wind," he said. The home is in L'Isle-Verte, a small town 450 kilometres (280 miles) northeast of Montreal with a population of around 1,400 people.

The town's acting Mayor Ginette Caron told a news conference that most residents of the home are reliant on caregivers.

She said these include elderly people needing "100 percent care, almost all in wheelchairs, using walkers, or who aren't mobile at all, people suffering from the late stages of Alzheimers.

"The types of services offered here are not found just anywhere. That's what we've also lost," she said.

Authorities said 23 people were evacuated from one third of the building. Thirteen of them were injured, one seriously, and were treated at nearby hospitals. Two firefighters were also hurt.

Fire chief Yvon Charron said his crew hopes to breach the remaining areas worst hit by the flames in the coming hours "to search for any bodies."

The Red Cross set up a makeshift shelter at a local school where several people rescued from the inferno spent the night, according to a representative, Myriam Marotte.

Some residents might have been away visiting family, or may have taken refuge elsewhere during the blaze and missed being counted, she told local television.